Uneasy Calm on Sudan-S.Sudan Border after U.N. Ultimatum

Sudan and South Sudan's armies were locked in a tense standoff Thursday hours after a U.N. Security Council ultimatum to end hostilities or face possible sanctions.

"We have no reports" of clashes or air strikes Southern army spokesman Philip Aguer said, after the U.N. body on Wednesday demanded the fighting stop within 48 hours.

Sudan's army "is still preparing to attack our positions... but there has been no fighting since Tuesday," Aguer said, warning that southern troops dug into fortified defensive positions along their volatile border were on full alert in case of renewed conflict.

Sudan and South Sudan have edged to the brink of all-out war in weeks of bloody clashes, which peaked in the South's seizure of the key Heglig oil field from Khartoum's army, before pulling back after international condemnation.

However, clashes and air strikes by Sudanese warplanes have continued since then, prompting the Security Council's ultimatum in New York late Wednesday.

With China and Russia joining the growing calls for an end to the border conflict, the 15-member council unanimously passed a resolution giving diplomatic muscle to African Union efforts to get peace negotiations started.

The council ordered the two sides to restart AU-mediated peace talks within two weeks. The resolution threatens additional non-military sanctions if either side fails.

"I think it's a very good resolution as it's going to sanction those who do not accept the decision... we already have," Southern Information Minister Barnaba Marial Benjamin said.

Warning of a looming "full scale and sustained war," U.S. ambassador Susan Rice told the council "both countries are on the brink of returning to the horrors of the past and threaten to take the entire region with them."

While still one country, north and south Sudan fought a two-decade civil war up to 2005 in which more than two million people died.

In New York, South Sudan's Minister for Cabinet Affairs Deng Alor Kuol offered his country's "solemn commitment" to follow the resolution.

But he appealed to the United Nations to "urgently mobilize humanitarian assistance for the population affected by Sudan's continuous aerial bombardments and ground incursions" into the South.

Sudan's U.N. ambassador Daffa-Alla Elhag Ali Osman expressed reservations about the resolution, however.

"Peace between the two republics, Sudan and South Sudan, will only be achieved by halting all forms of support and sheltering proxy rebel and armed groups espoused by South Sudan," Osman told the council.

But the South also said that while the border was calm Thursday, they feared renewed conflict and that Khartoum would not listen to U.N. demands.

"For the last two years, I have been reporting air bombarding, and I don't think Khartoum will stop with just U.N. wishes -- they have always denied bombing, but who else is it?" Aguer added.

"Wishes cannot work alone -- the U.N. should come and monitor the border."

Both sides accuse each other of arming rebel fighters as proxy forces to attack the other -- claims each side deny.

Aguer repeated claims Thursday that Sudan was "supplying arms and training militia against South Sudan."